It is currently 14F outside.  The sun shining brightly and there is a stiff wind.  I have come to expect some neat things from this house…

1 – The heat last went on about 20 minutes ago.  It will not come on again until the sun goes down.
2 – We’ll have 80 gallons of 100F+ solar heated hot water by the end of the day.

How great is that!

Some of you may know that I try to add any useful information I can to the forums on http://www.GreenBuildingTalk.com.  Two days ago I came across something that may prove to be very useful to us, and to anyone with a geothermal system and a desuperheater.

You may have read my previous posts about making how water.  Our ground source heat pumps don’t run much.  Because of this, the desuperheaters have never made “hot” water.  The best we had ever gotten is warm (~90F).  We may have found a way to make more hot water when the pumps are running.

We have Honeywell 8000 series thermostats.  There is a setting that determines how many times the thermostat is allowed to call for heat in a one house period.  This setting is called CPH (cycles per hour).  Our thermostats were previously set to “3”.  This meant that the GSHP could go on and off 3 times within a one hour period (if the thermostats called for heat – or cooling).  Who cares, right?  Well… This lead to relatively frequent starts and stops of the pumps (AKA short cycling).  The pumps would come on, put a little warm air into the house, and then shut off within a few minutes.  These short run times are hard on the equipment, and they also ensure that the equipment never reaches its normal operating temperature and maximum efficiency.  One other consequence is that the refrigerant gases never reach the high temperatures necessary to heat hot water.  As stated, the best we were ever getting is warm water.

Based on some information found in the forums, I have since reduced the CPH setting in the thermostat programming to “1”.  This means the thermostat is only allowed to run the heat pumps once per hour.  While the system can run for as long as it needs to run in order to satisfy the set temperature, even if it has to run the full hour (extremely unlikely with this house), it can only run once.  For instance, rather than running three 5 minute cycles in an hour, it may now only run one 15 minute cycle during that hour.  This change – appears – to be producing more hot water.  I will let you know for sure after I’ve had some time to let the system run while taking measurements prior to use (i.e. before showers or baths).

More on this later.

Ed
Mr. Green Dreams

PS – I don’t want to be a "Bah Humbug," but have you ever measured how much energy Christmas lights use?  WOW!  We have icicle lights outside, and a Christmas tree inside.  How about 500 watts!  As much as it pains me, we still turn them on.  However, they are on timers.  We’ll be doing some after Christmas shopping for closeouts on LED lights for next year.